1. Field of Invention
Aspects of the invention relate to an illumination device, a display device, and a projection type display device.
2. Description of Related Art
A related art liquid crystal display element, such as a liquid crystal panel and a liquid crystal light valve, can be used as a light modulation device in a direct-view type display device or a projection type display device. The liquid crystal display element is a so-called hold type display element that modulates intensity by controlling a quantity of transmitted lights per unit time. “Blurring” can be perceived in an edge portion of an image when moving images are displayed, and measures to improve this drawback are being discussed. See, for example, Taiichiro Kurita, “Hourudo-gata disupurei no hyouji houshiki to douga hyouji niokeru gashitsu” Proceedings of the First LCD Forum, the Japanese Liquid Crystal Society, August 1998, pp. 1-6.
To improve the quality of moving images in the liquid crystal display element, which is a hold type display element, adopting two techniques as follows is thought to be effective: (1) to improve a display characteristic of the liquid crystal display element itself, for example, by increasing a response speed of the display element through modifications of liquid crystal materials or technical devices in a driving circuit; and (2) to improve an illumination method of illuminating the liquid crystal display element, for example, by switching ON/OFF the illumination lights intermittently on time base and thereby shortening a display time.
Improvements of the image quality of moving images for the liquid crystal display device are proceeding with the focus on the modifications of liquid crystal materials or technical devices in the driving circuit. However, these efforts alone are not enough, and improvements of the illumination device and the illumination method need to be discussed actively, too. Because a discharge lamp widely used as a light source in the direct-view type display device or the projection type display device is not suitable for intermittent ON/OFF operations, there has been discussed an optical system that can achieve intermittent illumination by a disposing device of some kind for controlling illumination lights on the illumination optical path. See, for example, JP-A-2001-296841.